Halogen type filament lamp containing phosphorus and nitrogen

ABSTRACT

A tungsten-halogen cycle electric incandescent lamp has a fill including a phosphonitrilic halide. Mixtures of more than one of the halides may be employed. The halide can be introduced into the lamp envelope in solution, the solvent being evaporated thereafter to leave the halide as a residue.

United States Patent Johnston et al. 1 1 Aug. 5, 197 5 15 1 HALOGEN TYPEFILAMENT LAMP 2,882,435 4/1959 Millner et a1. 313/222 CONTAINING AND2.928977 3/1960 ROth et al. 313/222 NITROGEN 3,311,777 3/1967 Schroder313/222 X 3,465,193 9/1969 Beuvens et al.... 313/174 X [75] Inventors;Robert Bernard Johnston; John 3,712,701 1/1973 Johnston et a1 313/222 Xg i i Rees both of FOREIGN PATENTS OR APPLICATIONS an 763,062 7/1967Canada 313/222 173] AssIgnee: Thorn Electrlcal Industnes LImIted, OTHERPUBUCATIONS London, England Chem1cal Abstracts, Jam-June, 1967,-FormulaIndex, [22] Filed: Sept. 10, 1973 VOL 66, 950]; [2]] App} 395 0 ChemicalAbstracts, Jan..1une, 1967,Formula Index,

Vol. 66, p. 12F. Related US. Application Data Continuation of S812 N0.1,404, Jan. 8, 1970, Primary Examiner palmer Demeo abandoned- Attorney,Agent, or FirmRobert F. OConnell [52] US. Cl 313/174; 313/222 [57]ABSTRACT [51] Int. Cl H01 61/26; HOlk 1/50 A tungsten halogen cycleelectric incandescent p 174 22 2 [58] Fleld of Search 2 23 has a fillmcludmg a phosphomtrlllc hallde. MIxtures [56] References Cited of morethan one of the halides may be employed. The

halide can'be introduced into the lamp envelope in so- UNITED STATESPATENTS lution, the solvent being evaporated thereafter to 674,7545/1901 Blau 313/222 X leave the halide as a residue 1,249,978 12/1917MacKay 313/222 X 1.925.857 9/1933 van Liempt 313/222 x 4 Clams, 1 DrawmgFlgure PATENTEU M18 W5 ATTORNEY HALOGEN TYPE FILAMENT LAMP CONTAININGPHOSPIIORUS AND NITROGEN This is a continuation of application Ser. No.1,404, filed on Jan. 8, 1970, now abandoned.

The present invention relates to tungsten-halogen cycle electricincandescent lamps.

In operation of these lamps a halogen element,'usually either bromine oriodine acts in association with tungsten vapour evaporated from thefilament, to minimise deposition of tungsten on the envelope wall.

While allowing the use of compact and mechanically strong lampenvelopes, permitting pressure filling to several atmospheres, andincreased filament life, these lamps are more difficult to produce thanconventional incandescent lamps. Under therelatively high-temperaturesof operation of these lamps, impurities can be released which interferewith efficient working but it is difficult to introduce a getter forimpurities which will remain active after lamp processing but notinterfere with the regenerative cycle. Furthermore, whereas closecontrol of the quantityof halogenpresent is necessary in order toachieve optimum efficiency of the regenerative cycle, in known methodslosses of halogen can occur either through evaporation or by chemicalreaction or physical absorption either before or during lamp processingafter introduction of the halogen.

The present invention provides a means whereby the halogen can beintroduced as a substance which remains inert during lamp processing,but releases a predetermined quantity of halogen and provides agettering action upon thermal dissociation.

According to the present invention there is provided a tungsten-halogencycle electric incandescent lamp having a fill including aphosphonitrilic halide.

Mixtures of phosphonitrilic halides having different halogen atomsand/or different number of (PNY units, where Y is the halogen, in themolecule may be employed, such as a mixture of (PNBr and (PNBr Thephhosphonitrilic halides can be prepared by conventional techniques.

The halides are stable at room temperature. However, they can bedissociated into their elements by heating within the lamp envelope, forexample by operating the lamp. The halogen supports the regenerativecycle, and the phosphorus provides a gettering action.

Before the present invention, in the case of lamps having a fillincluding elementary bromine, precise control of the quantity of brominewas necessary in order to avoid corrosion of the tungsten filament byexcess bromine, which would lead to lamp failure. Although corrosioncould be reduced by introducing hydrogen with the bromine, as forexample as hydrogen bromine or as CHBr Cl-l Br or C HgBI', the hydrogentended to diffuse through the fused silica of the envelope, leading tothe formation of an excess of bromine. In the present invention, thephosphorus serves a function similar to that of hydrogen, when thehalogen is bromine, in that it inhibits the reaction between bromine andthe tungsten filament, but the disadvantage of a short lamp liferesulting from loss of hydrogen by diffusion is avoided.

The phosphonitrilic halides can be dissolved in inert solvents,preferably non-polar solvents such as benzene, ether, petroleum etherand chlorinated hydrocarbons, and can thus be introduced into the lampenvelope as a solution, for example by injection onto the filament orenvelope wall, facilitating close control of the quantity of halideintroduced. The solvent can be evaporated from the envelope, e.g. undera vacuum, leaving the halide-as a residue; Y

' For example a solution of a mixtureof trimeric and tetramericbromides, eg in benzene or a solution of a mixture of (PNCI2)4, and egin petroleum ether can be used.

The following are some examples of methods of making lamps in accordancewith the present invention.

1 EXAMPLE 1 In making a 12v. 100 w. compact projection lamp having aninternal volume of 0.65 cc.s approximately,

arid 0.035cc.s of the solution was injected into the lamp -'en\ elope.An exhaust/gas-filling apparatus was connec'ted to'the exhaust tube andthe envelope was evacuated, flushed with nitrogen and heated to a lowtemperature (about 150C) to evaporate the solvent of the solution.Thereafter the envelope was filled with an inert gas e.g. N Ar, Kr or Xeto the required pressure in the conventional manner and the exhaust tubewas sealed.

EXAMPLE II In making a 12v. 55 w. compact car lamp having an internalvolume of 0.65 cc.s approximately the procedure of Example I wasfollowed except that 0.024 cc.s of the solution was injected into thelamp envelope.

EXAMPLE III In making a 12v. 55w. compact car lamp having an internalvolume of 0.65 cc.s approximately the procedure of Example I wasfollowed except that 0.05 cc.s of a solution in petroleum ether of amixture of (PNCI L, (PNC1 PNCI and (PNCI containing 0.05 g. of themixture per cc.s of solution was injected into the lamp envelope insteadof the solution of mixed phosphonitrilic bromides.

The solution used in Example III has been found to be particularly wellsuited for lamps having a loading of less than 20w./cm. of internalenvelope wall area.

In the method described in the Examples the exhaust- /gas filling systemis not exposed to the corrosive action of halogens. Thus the need forthe usual corrosionresistant materials and frequent maintainance of thesystem can be avoided. In addition, the disadvantage ofhalogen-degradation of the lubricants employed, leading to a reductionin the life of the vacuum pumps, can be avoided.

Whereas before the present invention specialised procedures for handlingand processing the components for tungsten-halogen lamps were required,the procedures for making lamps according to the invention as describedin the examples are more similar to those for making conventionalelectric incandescent lamps, because of the gettering action of thephosphorus released on dissociation of the halides. As a result of theaccuracy with which the halogen can be introduced, a lower standarddeviation in the lamp life may also be achieved. In addition, a longerlamp life may be obtained. The present invention also allows use ofuseof less expensive materials, containing greater amounts of impuritiesthan were hitherto practicable, to be used for the lamp envelopes, asfor example high melting point glasses, or Vycor (approximately 96percent silicon glass), instead of the more usual high purity fusedsilica envelopes.

The accompanying drawing illustrates an example of one form of lampprepared as described in Example 1. Referring to the drawing, the lamphas a high melting point glass envelope 1 provided with an aperture 2through which the lamp was exhausted and filled. The lamp was thereaftersealed by sealing off an exhaust tube 3 with which the aperture 2 isprovided. The envelope has two lead-in wires 4 sealed therethrough,connected to a tungsten filament 5.

We claim:

1. An electric incandescent lamp comprising: a closed light-transmittingenvelope of a high temperature-resisting material;electrically-conducting lead-in wires sealed through said envelope; atungsten filament inside said envelope connected to said lead-in wires;and a fill inside said envelope comprising an inert gas and the productsresulting from the thermal dissociation of a phosphonitrilic halidecomprising (PNY where n is an integer and Y is Br or Cl, said fillthereby releasing a predetermined amount of said Br or C1 to produce aregenerative cycle and releasing a predetermined amount of said P toproduce a gettering action and to inhibit the reaction of said Br and Clwith said tungsten filament.

2. A lamp according to claim 1 wherein said phosphonitrilic halideincludes a mixture of (PNBr and (PNBr- 3. A lamp according to claim 1wherein said phosphonitrilic halide includes a mixture of (PNCI (PNCl(PNCl and (PNCl 4. An electric incandescent lamp comprising: a closedlight transmitting envelope of a high temperature-resisting material;electrically-conducting lead-in wires sealed through said envelope; atungsten filament inside said envelope connected to said lead-in wires;and a fill comprising an inert gas and nitrogen, phosphorus and ahalogen, said nitrogen, phosphorus and halogen having being formed bythermal dissociation of a phosphonitrilic halide.

1. An electric incandescent lamp comprising: a closed light-transmittingenvelope of a high temperature-resisting material;electrically-conducting lead-in wires sealed through said envelope; atungsten filament inside said envelope connected to said lead-in wires;and a fill inside said envelope comprising an inert gas and the productsresulting from the thermal dissociation of a phosphonitrilic halidecomprising (PNY2)n, where n is an integer and Y is Br or Cl, said fillthereby releasing a predetermined amount of said Br or Cl to produce aregenerative cycle and releasing a predetermined amount of said P toproduce a gettering action and to inhibit the reaction of said Br and Clwith said tungsten filament.
 2. A lamp according to claim 1 wherein saidphosphonitrilic halide includes a mixture of (PNBr2)3 and (PNBr2)4.
 3. Alamp according to claim 1 wherein said phosphonitrilic halide includes amixture of (PNCl2)4, (PNCl2)5, (PNCl2)6, and (PNCl2)7.
 4. AN ELECTRICINCANDESCENT LAMP COMPRISING A CLOSED LIGHT TRANSMITTING ENVELOPE OF AHIGH TEMPERATURE-RESISTING MATERIAL, ELECTRICALLY-CONDUCTINGLEAD-IN-WIRES SEALED THROUGH SAID ENVELOPE, A TUNGSTEN FILAMENT INSIDESAID ENVELOPE CONNECTED TO SAID LEAD-IN WIRES, AND A FILL COMPRISING ANINERT GAS AND NITROGEN, PHOSPHORUS AND A HALOGEN, SAID NITROGEN,PHOSPHORUS AND HALOGEN HAVING BEING FORMED BY THERMAL DISSOCIATON OF APHOSPHONITRILLIC HALIDE.